Gas analysis



J. c. PETERS, JR

GAS ANALYSIS Filed Jan. 5. 1924 Aug. 12 1924.

INVENTOR. 0. 0w) BY :4 6151/ Ak ATTORNEY.

Patented Aug. 12, 1924.

UNITED STATES,

"PATENTgermamcon c. mans, J'R., or STATE coLLEen, PmsYLvAm'assmNon r0LEEDS a nommwr COMPANY, or rmmnnnrnm, rnnnsynvama, a CORPORATION orPENNSYLVANIA.

GAB manger s Application filed January 3,1924. Serial R o." 684,133{

My invention relates to analysis-of gases for determ ning, measuring,record1ng,'or

effectingacontrol in response to changes of the amount of one or'moreparticular gases in a gas mixture.

In practicing myinvention,there is utilized-theknown method of gasanalysis depending upon changes 'in' thermal conductivity of the gaswithreference to the conductivity. of a standard gas, as measured ordetermined by changes'of resistance of a conductor disposed .in'a cellor chamber through which the gas to-be analyzed is passed,with-reference to the, simultaneous resistance of a. conductor similarlyplaced in another cell or chamber containing. the standard gasq' Inaccordance with my 'invention, particu-' 'larly for the continuousanalysis of gases, a'

small fraction of the gas tobe analyzed is passed through the gas cellbyconvection effected by heat liberated from the conductor 7 in the cell,preferably from and back to the -main supply. or current of gas to beanalyzed, and preferably from and'back to points located substantiallyin the same plane normal to the axis of flow of the main-supply of gas.Further in accordance with my invention, provided means for correctin orcurrent which heats the conductors disposed in the gas cells.

Further-in accordance with my invention, means are provided forcorrecting or compensating for changes in temperature of the airsurrounding the cells.

Furtherin accordance with my invention, means are providedfor-correcting or compensating for permanent changes in the re-'sistance of the conductors in the cells.

My invention resides in the method and features of structure andcombination ofthe character hereinafter described and claimed.

For an illustration of one of the various forms my invention 'may take,reference is to be had to the accompanying drawing, in which: 1 I I Fig.1 is a side elevational view of the cells and the connections of one ofthem to the gas conduit. V

Fig. 2 is-avertical'sectionalview, partly 1, taken on the line 2 2 ofFig. 3.

Fig. 3' is a'horizonta'l sectional view taken on the line 3-'3 ofFig. 1. I

Fig; a. is a diagrammatieview of a circuit arrangement 'in'accordancewith my invention.

Referring to the draw'ing,.A is block of ,metal or other suitablematerial having therein the cells or chambers. B and C. Or

in elevation, of the structure shown in Fig.-

the cells B andC may be in separate blocks;

or members} Extending. longltudinally of the cells BandC are theresistance conductors R and B, respectively, of any suitable materialhaving substantial temperature co- R arefine. platinum wires, which mayhave diameters ofjthe order of two mils. At their upper ends they aresoldered ate and b, respectively, to the wires 0 and d, respecefiicient."Preferably the conductors R and 7 5 tively, of gold'or other suitablematerial ex tending through the insulating members e and f, forminggas-tight end closures for the cells 'B and C,-re'spectively. At theirlower ends the conductors R and R are 501 dered at g and h,respectively, to the metallic springs-i and j, respectively,=which arepreferably of gold or other material chemically neutral with respectto'the gases involved. The springs c and 7' keep the conductors R and Rtaut, and are connected to the conductorsm and n, of gold orvothersuitable material, sealed in the end closure members o'and p,respectively, for the cells B and C. The closure members 0 and 'p-may beof glass or other suitable insulating material, or the lower ends of thesprings 11 and j may becon- *nected to metal end closures of the cells Band C when the block is of metal, as indicated. It will be understoodthat either a rrangement may be utilized, as ma be suitable orconvenient. With the con uctors m and n connect conductors and r, foreffecting connection of the resistance conductors R and R in aVVheatstone bridge or other suitable circuit arrangement. When thesprings 2' and are connected to metallic end closures 0 an '72 asdescribed, the external conductors g and 'r are not required, and thebridge connection may be made directly to the block A.

The gas to be analyzed flows through the conduit or pipe D in suitabledirection, preferably in the direction of the arrow, Fig. 2. Connectionis made from the conduit D to the lower end of the chamber B by theshort tube a and from the upper end of the chamber B connection is madethrough the long tube t to the conduit D at a point longitudinally inthe latter preferab y substantially identical with the location of theconnection 8. The two points of connection of the cell or chamber B tothe conduit D are preferably in the same plane normal to thelongitudinal axis of the conduit D. It will be understood that theconduit D need not be parallel with either of the chambers B or C, butmay extend at right angles to them or be in any other way suitablydisposed or arranged.

The resistance wires R and R are connected in circuit as indicated inFig. 4, which illustrates a Wheatstone bridge. In a conjugate conductorof the Wheatstone bridge are included the source of current- S, whichmay be of any suitable type, as a battery, the adjustable resistance orrheostat w and the ammeter E, the rheostat u serving to adjust and theammeter E serving to indicate or measure the magnitude of the currentpassed from the source S through the bridge arms, in two of which areconnected, respectively, the resistance wires R and R there beingutilized in the arm with the resistance wire R an additional resistance1:. The conductors r and g are connected together at a point of junctionforming one end of the second conjugate conductor which includes thegalvanometer G and whose other terminal is at the contact w movablealong the resistance R divided by the contact to into portions disposed,respectively, in the other two arms of the bridge, in one of which areincluded the resistances R and m, and-in the other of which is connectedthe resistance R with the resistance y shunted by the variableresistance a.

While, as above stated the resistance wires R and R possess substantialtemperature oo-efiicients, it is preferred that the resistances R R, R,v, y and a shall have substantially zero temperature coefficients, andto this end they may be made of manganin or equivalent material. Theresistance w, however, has a temperature coefficient, and may beconstructed of nickel wire.

The operation is as follows:

The as or gas mixture flows through the con uit D and a ortion of itcirculates through the cell B y convection due to the heat liberated bythe resistance R. The gas enters the cell B throu h the tube a, ascendsthrough the cell E, and passes through the tube 13 back to the conduit Dto a point therein similar to that from which the connection a is taken.By so relying upon convection for circulating the gas through the cellB, the amount of gas circulated through the cell is independent of thepressure of the gas within the conduit D and is also independent of thevelocity of the gas through the conduit D. Accordingly, the apparatus isrendered free of error due to changes in quantity or rate of flow of gasthrough the cell B such as would be due either to changes in thepressure or velocity of the gas flowing through the conduit B. Inaccordance with my 1nve-ntion, therefore, the maintenance of asubstantially constant rate of flow of the gas, for example, twenty-twocubic centimeters er minute, according to the Bureau of standardsmethod, is dispensed with, nor is there need for recourse to a methodinvolving a diffusion orifice for effecting continuous change of the gaswithin the cell B.

The current passing from the source S through the resistance wires R andR having been adjusted by rheostat u to a predetermined magnitude,indicated by the ammeter E, for which the apparatus is calibrated, thecontact 10 is moved backward or forward over the resistance R to suchposition as will cause a mil deflection of the galvanometer G. Shouldthe amount of a particular gas or particular mixture of gases in themixture of gases passing through the conduit D change, the bridge willbe unbalanced, because of the change in thermal conductivity of the gascirculating through the chamber or cell B, the efiect of change ofthermal conductivity of the gas causing a change in the temperature andtherefore in the resistance of wire R, since the amount of heat suppliedto the wire by the electric current is substantially constant. There isa consequent unbalancing of the bridge, which may be rebalanced bymoving the contact to to a. new and proper position upon the resistanceR, with which may be associated a scale calibrated in terms of theamount of the particular gas or gases whose amount is to be determined.

It is practically impossible to construct the resistance wires ofconductors R and R so that they shall be identical, and it is similarlypractically impossible to construct the cells themselves so that theycrate identically as regards radiation, heat conduction, etc., with theresult that changes in value of the heating current passing through theconductors R and R introduce errors which diminish the accuracy ofmeasurement. To correct for errors caused by changes in value of theheating current, there is introduced into'one of the bridge arms, asthat including the conductor R, a resistance '0 of such magnitude thatin combination with its associated resistance R the resistance in thatarm of the bridge is one having in effect a different temperaturecoefficient from the resistance wire R itself. This is due to the factthat the temperature co-efficient of the resistance '0 is' differentfrom that of the conductor R with which it is associated, and,accordingly, changes in resistance of the conductor R due to changes inits temperature have less effect on the change of the total resistanceof the bridge arm than in case the resistance '0 were omitted. Asstated, the resistance '0 preferably has very small or zero temperatureco-efiicient, and therefore the effective or over-all temperatureco-efficient of all the resistance in the bridge arm including R and 'vis in effect reduced, and therefore less affected by changes inmagnitude of the heating current. It will be understood that theresistance '0 may be placed in the other bridge arm with the conductor Ror resistances having the purpose of resistance *0 may be included inboth adjacent bridge arms containing conductors R and B. By recourse tothe resistance 0 as described, there results a combination with theresistance R, for example, having in effect a temperature coefficientdifferent from that of the resistance R alone, and the total resistancein the bridge arm varies with change in heating current at the same ratethat the resistance, as R, in the other bridge arm changes, whereby theerrors due to changes in magnitude of heating current are reduced oreliminated. The magnitude of the resistance n is accordingly made suchthat the unbalance of the bridge due to deviations from the normalmagnitude of heating current is a minimum, particularly with regard tothe nature of the gas to be analyzed or the nature and amount of theparticular gas whose quantity is to be determined.

In rior practice the cells correspondingto the ce ls B and C were placedin an air bath held with considerable difficulty at constanttemperature, and it was necessary that that temperature shouldcorrespond substantially with the temperature at which the instrument asa whole was calibrated. To avoid the necessity for such air bath and itsattendant disadvantages and difficulties, I introduce into a suitablearm of the bridge a shall opresistance on, of suitable magnitude andhaving a suitable temperature co-efiicient, as a positive temperatureco-eflicient correspondmg, for example, with nickel. The reslstance issubjected to the temperature of the ambient atmosphere, and accordinglyrises and falls in tem erature therewith, and in so rising and fallingin temperature it increases and decreases the resistance in the bridgearm in which it is included in extent to correct or compensate forvariations in atmospheric temperature. By use of the resistance w, theminimum unbalance of the bridge due to changes in atmospherictemperature is procured, as regards the particular gas and its amount asto which the analysis is to be effected. While the resist-,

ance m is indicated in Fig. 4 as present in a particular-bridge arm, itshall be understood that it may be placed in series with the resistancewire R which co-acts with the gas to be analyzed. Occasions might arise,however, that would require the inclusion of the resistance at in thebridge arm with the resistance R, or with the resistance R which latteris the resistance which co-acts with the standard gas, such as air orthe like, sealed and maintained in the cell C.

Correction for errors due to permanent changes in the apparatus, such,for example, as permanent changes in either or both of the resistancewires R and R are compensated for by the resistance e shunted by theadjustable resistance a. The resistance y, with its variable shunt 2,may be placed in any arm of the bridge.

The corrections or compensations above described, particularly thoseeffected by the resistances o, :0, 3 and 2, will in general be ofadvantage; and they are of great advantage for cases where the amount ofa particular gas or gases in the mixture passing through the conduit Dfluctuates Within a small range.

It will be understood that the galvanometer G may control a recorder ora control apparatus which may be utilized for effecting any suitablecontrol, as, for example, for changing or controlling the mixturepassing through the conduit D so as to maintain it substantiallyconstant as regards the particular gas or gases whose amount it isdesirable shall be maintained substantially constant. For example, thepointer or needle of the galvanometer G may control recorder mechanismof the character disclosed in Leeds Patent No. 1,125,699, in which casethe relative movement between thecontact w and resistance R is effectedby the recorder mechanism to effect rebalancing of the circuit, and therelative movement for such balancing is the movement which istransmitted to the recorder pen or marker.

The galvanometer G may be similarly utilized for controlling a controlmechanism of any suitable character. For example, the galvanometerneedle may control a mechanism of the character disclosed in said Leedspatent, in which case the contact w may be set to a desired positionupon the resistance R corresponding with the desired amount of theparticular gas or gases of the mixture traversing the conduit D, and themovement of the movable structure of the control mechanism will efiectchange in the amount of the particular gas or gases in such direction asto cause a rebalance of the Wheatstone bridge.

By way of example merely, it ma be stated that it may be desirab e tofin the percentage or amount of S0,, 00,, H 0,, or other gas in mixturewith air or other gas or gases, and for this purpose the meth 0d andapparatus herein escribed are useful. When a recorder is utilized asabove described, it will draw a curve representative of the percentagesor amounts of the particular gas or gases present in a current of amixture containing it or them. Or it may be desirable that the amount ofS0 for example, in mixture with air or other gas or gases, shall bemaintained substantially constant, in which case the control mechanismwill control the admission of SO at such rate or in such quantity as tomaintain the percentage of this gas in the mixture constant orsubstantially constant. In those cases where the percentage or amount ofthe particular gas in a mixture does not vary over wide limits, butremains within a range of a few per cent, the corrections orcompensations effected by the resistances o and m are substantiallyperfect, but less so when the percentage'of the particular gas varieswithin a wider range.

While I have hereinbefore referred to gas as undergoing test oranalysis, it shall be understood, with respect to the appended claims,that the term gas includes gaseous fluid in general, as permanent gas orvapor, or mixtures of gas and vapor.

What I claim is:

1. In the art of gas analysis, the method of procuring a sample fromanenclosed current of the gas to be analyzed, which comprises efi'ectingpassage of the gas substantially solely by convection from and back topoints in said current between which the pressure diflerence issubstantially nil.

2. In the art of gas analysis, the method which comprises eflectingsubstantially solely by convection a current of a sample of the gas tobe analyzed from and back to points in a moving mass of the gas betweenwhich the pressure difi'erence due to the gas velocity is substantiallynil;

3. In the art of gas analysis, the method which comprises efiectingsubstantially solely by convection a current of a sample of the. as tobe analyzed from and back to points ying substantiall in the same planenormal to the axis of ow of a stream of the s to be analyzed.

4. n the art of gas analysis, the method of procuring a sample from acurrent of the gas to be analyzed, which comprises heating a conductorby passing an electric current therethrough, an utilizing evolved heatfor efi'ectm passage of the gas ast said conductor y convection from t ecurrent of gas from and back to points in said current between whichthere is substantially no difference in pressure.

5. In the art of gas analysis, the method which comprises heating aconductor by passing an electric current therethrough, and utilizingevolved heat for producing a convection current of a sam le of the gasto be analyzed past said con uctor from and back to points insubstantially the same plane normal to the axis of flow of a stream ofthe gas to be analyzed.

6. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas to be tested or analyzed passes, a cell, means in saidcell responsive to changes in thermal conductivity of the gas, and meansproducing by convection a current of gas from said conduit through saidcell.

7. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas to be tested or analyzed passes, a cell, means in saidcell responsive to changes in thermal conductivity of the gas, and meansproducing by convection a current of gas from said conduit through saidcell back to said conduit.

8. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas to be tested or analyzed passes, a cell through which asample of the gas is to be circulated, and means in said cell evolvingheat to produce a convection current of gas from said conduit throughsaid cell.

9. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas to be tested or analyzed passes, a cell through which asample of the as is to be circulated, and means in said cel responsiveto changes in conductivity of the gas and evolving heat to produce byconvection a current of gas from said conduit through said cell.

10. Apparatus for testing or anal zing gas comprising a conduit throughwhic the gas to be tested or analyzed passes, a cell, connectionsbetween points in said conduit substantially in the same plane normal tothe longitudinal axis of said conduit and separated points in said cell,and means for heating the gas in said cell to effect a convectioncurrent therethrough.

11. Apparatus for testing or anal zing gas comprising a conduit throughwhic the gas to be tested or analyzed passes, a cell,

connections between points in said conduit substantially in the sameplane normal to the longitudinal axis of'said conduit and points in saidcell disposed at different altitudes, and means for heating the gas insaid cell to effect a convection current therethrough.

12. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas to be tested or analyzed passes, a cell, a conductordisposed therein, means for passing an electric current through saidconductor, and connections between points in said conduit substantiallyin the same plane normal to the longitudinal axis of said conduit andseparated points in said cell.

13. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas to be tested or analyzed passes, a cell, a conductordisposed therein and having a substantial temperature co-efiicient,means for passing an electric current through said conductor,connections between points in said conduit substantially in the sameplane normal to the longitudinal axis of said conduit and separatedpoints in said cell, and means responsive to changes in resistance ofsaid conductor.

14. Apparatus for testing or analyzing gas comprising a cell, aresistance conductor disposed therein, and a gold spring in circuit withsaid conductor in said cell holding said conductor taut.

15. Apparatus for testing or analyzing gas comprising a cell, aresistance conductor therein having a substantial temperatureco-efiicient, a source of current in circuit with said conductor forpassing heating current therethrough, and a resistance in circuit withsaid conductor for reducing error due to change in the magnitude of saidcurrent.

16. Apparatus for testing or analyzing gas comprising a plurality ofcells, one of said cells containing a standard gas and another of saidcells traversed by a current of the gas to be tested'or analyzed,resistance conductors disposed, respectively, in said cells and eachhaving a substantial temperature co-efiicient, a Wheatstone bridge indifferent arms of which said conductors are connected, a source ofcurrent for de livering heating current through said conductors, and aresistance in series with one of said conductors in the same bridge armtherewith for minimizing the effects of change in magnitude of thecurrent traversing said resistance conductors.

17. Apparatus for testing or analyzlng gas comprising a plurality ofcells, one of said cells containing a standard gas and another of saidcells traversed by a current of the gas to be tested or analyzed,resistance conductors disposed, respectively, in said cells and eachhaving a substantial temperature co-efiicien't, a Wheatstone bridge indifferent arms of which said conductors are connected, a source ofcurrent for delivering heating current through said conductors, and aresistance having substantially zero temperature co-efiicient connectedin series with one of said resistance conductors in the same bridge armtherewith for mini mizing the effects of change in magnitude of thecurrent traversing said resistance conductors.

18. Apparatus for testing or analyzing gas comprising a plurality ofcells, one of said cells containing astandard gas and another of saidcellstraversed by a current of the gas to be tested or analyzed,resistance conductors disposed, respectively, in said cells and eachhavin a substantial temperature co-eflicient,a eatstone bridge indifferent arms of which said conductors are connected, a source ofcurrent for delivering heating current through said conductors, and aresistance connected in an arm of said bridge and having such magnitudeand a temperature co-efiicient of such magnitude as to substantiallycompensate for changes in temperature of the atmosphere surrounding saidcells.

19. Apparatus for testing or analyzing gas comprising a plurality ofcells, one of said cells containing a standard gas and another of saidcells traversed by a current of the gas to be tested or analyzed,resistance conductors disposed, respectively, in said cells and eachhaving a substantial temperature co-eflicient, a Wheatstone bridge indifferent arms of which said conductors are connected, a source ofcurrent for delivering heating current through said conductors, and aresistance connected in an arm of said bridge and having a magnitude forsubstantially compensating for permanent changes in the resistance ofone or more of said resistance conductors.

20. Apparatus for testing or analyzing gascomprising a plurality ofcells, one of said cells containing a standard gas and' another of saidcells traversed by a current of the gas to be tested or analyzed,resistance conductors disposed, respectively, in said cells and eachhaving a substantial temperature co-eificient, a Wheatstone bridge indifferent arms of which said conductors are connected, a source ofcurrent for delivering heating current through said conductors, and aresistance connected in an arm of said bridge and having a magnitude forsubstantially compensating for permanent changes in the resistance ofone or more of said resistance conductors, said resistance comprisinga-resistance shunted by a variable resistance.

21. Apparatus for testing or analyzing gas comprising a conduit throughwhich the gas tobe tested or analyzed passes,'a cell, means in said cellafi'ectedby changes inthermal conductivity of the gas, and; means forproducing by convection a car- 5 rent of gas from said conduit throughsaid cell comprising gas connections from said cell to points in saidconduit between which thle difference in pressure is substantially n1 Intestimony whereof'I have hereunto 1 aflixedmy signature this 31st day ofDecember, 1923.

JACOB o. PETERS, JR.

